Vacuum machine, compressor, and piston

ABSTRACT

A vacuum machine includes: a crankcase; a cylinder body fixed to the crankcase; a cylinder head fixed to a distal end of the cylinder body; and a piston reciprocating within the cylinder body, wherein the piston includes: a piston rod; a piston head fixed to a distal end of the piston rod and defining a chamber in cooperation with the cylinder body and the cylinder head; and a check valve arranged within a space formed between the piston rod and the piston head, the piston rod and the piston head each includes a through-hole communicating with the space, and the check valve is elastically deformable within the space so as to open and close one of the through holes of the piston rod and the piston head.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-171862, filed on Aug. 26, 2014, and the prior Japanese Patent Application No. 2014-171875, filed on Aug. 26, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND

(i) Technical Field

The present invention relates to a vacuum machine, a compressor, and a piston.

(ii) Related Art

There are known a vacuum machine and a compressor in which a piston reciprocates. In some cases, a distal end of the piston is formed with a through-hole, and a check valve opening and closing this through-hole is fixed to a piston. This check valve is repeatedly and elastically deformed to open and close the through-hole in conjunction with the reciprocation of the piston. Japanese Patent Application Publication No. 2008-95700 discloses a related device.

When such a check valve is greatly elastically deformed repeatedly, the durability of the check valve might deteriorate. Also, when the check valve is deformed greatly, it might be plastically deformed to exceed its elastic limit, so that the through-hole cannot be closed adequately.

SUMMARY

According to an aspect of the present invention, there is provided a vacuum machine including: a crankcase; a cylinder body fixed to the crankcase; a cylinder head fixed to a distal end of the cylinder body; and a piston reciprocating within the cylinder body, wherein the piston includes: a piston rod; a piston head fixed to a distal end of the piston rod and defining a chamber in cooperation with the cylinder body and the cylinder head; and a check valve arranged within a space formed between the piston rod and the piston head, the piston rod and the piston head each includes a through-hole communicating with the space, and the check valve is elastically deformable within the space so as to open and close one of the through holes of the piston rod and the piston head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a vacuum machine;

FIG. 2 is a side view of the vacuum machine;

FIG. 3 is a rear view of the vacuum machine;

FIG. 4 is a partial enlarged view of FIG. 3;

FIG. 5 is a partially sectional view of a vacuum machine according to a comparative example;

FIG. 6 is front view of a compressor;

FIG. 7 is a rear view of the compressor;

FIG. 8 is a partially enlarged view of FIG. 7; and

FIG. 9 is a partially sectional view of a compressor according to a comparative example.

DETAILED DESCRIPTION

FIGS. 1, 2, and 3 are front, side, and rear views of a vacuum machine A, respectively. Additionally, FIGS. 1 and 3 illustrate a partial section. The vacuum machine A includes: four cylinders 10 a to 10 d; a crankcase 20 to which the four cylinders 10 a to 10 d are fixed; and a motor M arranged on an upper portion of the crankcase 20. The cylinders 10 a to 10 d are fixed around the crankcase 20. The cylinder 10 a includes: a cylinder body 12 a fixed to the crankcase 20; and a cylinder head 15 a fixed to the cylinder body 12 a. A partition plate 14 a intervenes between the cylinder body 12 a and the cylinder head 15 a. Likewise, the cylinders 10 b to 10 d include cylinder bodies 12 b to 12 d and cylinder heads 15 b to 15 d, respectively. Between the cylinder bodies 12 b to 12 d and the cylinder heads 15 b to 15 d, partition plates 14 b to 14 d intervene, respectively. The partition plates 14 a to 14 d are examples of partition wall portions. The cylinder 10 a and the like and the crankcase 20 are made of metal such as aluminum with good heat radiation. A nozzle N is fixed to the crankcase 20. The nozzle N exhausts air introduced into the crankcase 20 to the outside. Also, apertures Hal and Hat are provided in the cylinder head 15 a. Likewise, apertures Hb1, Hb2, Hc1, Hc2, Hd1, and Hd2 are provided in the cylinder heads 15 b to 15 d, respectively.

The motor M illustrated in FIG. 2 includes coils not illustrated, a rotor 40, a stator not illustrated, and a printed circuit board PB. The stator is fixed to the crankcase 20. Around the stator, plural coils are wound. The coils are electrically connected to the printed circuit board PB. The stator is excited by energizing the coils. The rotor 40 includes a rotational shaft 42, a yoke 44, and one or more permanent magnets not illustrated. The rotational shaft 42 is rotatably supported by plural bearings arranged within the crankcase 20. The yoke 44 is fixed to the rotational shaft 42, and the yoke 44 rotates with the rotational shaft 42. The yoke 44 has a substantially cylindrical shape, and is made of metal. One or more plural permanent magnets are fixed to an internal circumferential surface of the yoke 44. The permanent magnet faces an outer circumferential surface of the stator. The stator is excited by energizing the coils. Thus, the magnetic attractive force and the magnetic repulsive force exert between the permanent magnet and the stator. This magnetic force causes the rotor 40 to rotate. Thus, the motor M is a motor of an outer rotor type in which the rotor 40 rotates.

A fan F is fixed to the yoke 44 of the rotor 40, and rotates with the rotor 40. Thus, the crankcase 20 and the cylinders 10 a to 10 d are cooled. Also, an increase in temperature depending on friction of moveable portions can be suppressed.

Next, the internal structure of the cylinder 10 a will be described. As illustrated in FIG. 3, the cylinder body 12 a is fixed to an outer peripheral wall of the crankcase 20 to communicate with a hole formed in the outer peripheral wall of the crankcase 20. Also, the cylinder head 15 a is fixed to a distal end of the cylinder body 12 a through the partition plate 14 a. A chamber 13 a is formed in the cylinder body 12 a. The chamber 13 a is defined by the cylinder body 12 a, a distal end of the piston Pa, and the partition plate 14 a. The piston Pa reciprocates in conjunction with the rotation of the motor M, so a capacity of the chamber 13 a increases and decreases. A proximal end of the piston Pa is located within the crankcase 20, and is coupled with the rotational shaft 42 receiving rotary power through a bearing from the motor M. Specifically, the proximal end of the piston Pa is coupled at the eccentric position with respect to the central position of the rotational shaft 42, and the piston Pa reciprocates in conjunction with the one-way rotation of the rotational shaft 42. Pistons not illustrated and moving within the other cylinders 10 b to 10 d are provided therewithin, respectively. As for these pistons, positional phases are shifted at intervals of 90 degrees. These pistons reciprocate to introduce air into the cylinders 10 a to 10 d and the crankcase 20 through the aperture Ha1, Hb1, Hc1, and Hd1, which exhausts air from the nozzle N.

Next, the inner structure of the cylinder 10 a will be described in detail. FIG. 4 is a partially enlarged view of FIG. 3. The cylinder head 15 a includes: rooms 18 a and 19 a partitioned from each other; and the apertures Hal and Ha2 respectively communicating with the rooms 18 a and 19 a. The partition plate 14 a is formed with a hole portion 16 a communicating the room 18 a with the chamber 13 a. Note that the partition plate 14 a is not formed with a through-hole communicating the room 19 a and the chamber 13 a. However, the through-hole communicating the room 19 a with the chamber 13 a may be formed and sealed.

A check valve V1 is fixed to the partition plate 14 a. The check valve V1 allows air to flow into the chamber 13 a through the hole portion 16 a from the room 18 a, but restricts air from flowing reversely. The check valve V1 is fixed to an inner surface of the partition plate 14 a facing the piston head 25 a by a screw S1. A proximal end of the check valve V1 is fixed to the partition plate 14 a by the screw S1, a distal end of the check valve V1 is a free end, and the check valve V1 is elastically deformed to open and close the hole portion 16 a. The check valve V1 is elastically deformed by a difference in inner pressure between the chamber 13 a and the room 18 a, so the hole portion 16 a is opened and closed. The check valve Vi is arranged within the chamber 13 a. The check valve V1 is made of metal such as a stainless steel, but is not limited to this.

The piston Pa includes: a piston rod 21 a having a proximal end coupled with the rotational shaft 42; and a piston head 25 a fixed to a distal end of the piston rod 21 a by a screw not illustrated. A sealing ring C is sandwiched between the piston rod 21 a and the piston head 25 a. The sealing ring C seals between the piston Pa and an inner side surface of the cylinder body 12 a, and is made of material such as fluoric resin with a good self-lubrication property.

A space SP is formed between the distal end of the piston rod 21 a and the piston head 25 a.

Specifically, a recess portion 23 a is formed in the distal end of the piston rod 21 a, and a stepped portion 24 a is formed around the recess portion 23 a. The piston head 25 a is fitted into and fixed to the stepped portion 24 a. A through-hole 26 a communicating with the space SP is formed in the piston head 25 a. A through-hole 22 a communicating with the space SP is formed in the piston rod 21 a.

A check valve V2 is fixed to an inner surface, of the piston head 25 a facing the recess portion 23 a of the piston rod 21 a, by a screw S2. The screw S2 is an example of a fixation member. A proximal end of the check valve V2 is fixed to the piston head 25 a by the screw S2, a distal end of the check valve V2 is a free end, and the check valve V2 is elastically deformed to open and close the through-hole 26 a. The check valve V2 is elastically deformed by a difference in inner pressure between the chamber 13 a and the crankcase 20, so the through-hole 26 a is opened and closed. The check valve V2 is provided within the space SP and is elastically deformable therewithin. The check valve V2 permits air to flow into the crankcase 20 through the through-hole 26 a, the space SP, and the through-hole 22 a from the chamber 13 a, but restricts air from reversely flowing. The check valve V2 is made of metal such as stainless steel, but is not limited to this. The check valve V2 is a member that has a plate shape having a certain thickness so as to be elastically deformable.

When the reciprocation of the piston Pa causes the capacity of the chamber 13 a to increase from the minimum to the maximum, air is introduced into the room 18 a through the aperture Ha1 from the outside, and the distal end of the check valve V1 is elastically deformed to be bent away from the hole portion 16 a, which opens the hole portion 16 a. Thus, air is introduced into the chamber 13 a. When the capacity of the chamber 13 a decreases from the maximum to the minimum, the distal end of the check valve V2 is elastically deformed to be bent away from the through-hole 26 a and opens the through-hole 26 a, which introduces air from the chamber 13 a to the crankcase 20 through the through-hole 26 a, the space SP, and the through-hole 22 a. Additionally, at this time, the check valve V1 is kept closing the hole portion 16 a by the inner pressure of the chamber 13 a. In this way, air is introduced into the crankcase 20 through the chamber 13 a from the outside by the reciprocation of the piston Pa. Note that the pistons respectively arranged within the cylinders 10 b to 10 d have the similar structure. Thus, air is introduced in the crankcase 20 from the outside by the reciprocation of these pistons.

As illustrated in FIG. 4, the check valve V2 is arranged between the distal end of the piston rod 21 a and the piston head 25 a. Thus, when the distal end of the check valve V2 is elastically deformed to be bent away from the through-hole 26 a, the distal end of the check valve V2 abuts with a bottom surface of the recess portion 23 a, so that the check valve V2 is restricted from being further elastically deformed. Thus, the maximum amount of the elastic deformation of the check valve V2 is restricted to a certain amount. For example, when the great elastic deformation is repeated in such a check valve V2, the durability of the check valve might deteriorates. Also, when the check valve is deformed greatly, it might be plastically deformed to exceed its elastic limit, so that the through-hole cannot be closed adequately. Thus, the performance of the check valve might deteriorate. In the present embodiment, the check valve V2 is arranged between the piston rod 21 a and the piston head 25 a, and the elastic deformation amount is restricted by the piston rod 21 a. This can suppress the deterioration in the performance of the check valve V2 caused by a too large amount of the elastic deformation.

Also, the through-hole 22 a releases the screw S2 fixing the check valve V2 to the piston head 25 a. Specifically, the through-hole 22 a is formed coaxially with the screw S2 so as not to interfere with a head portion of the screw S2 protruding to the space SP. Thus, regardless of the protruding amount of the screw S2, the thickness of the space SP can be designed. Therefore, for example, the thickness of the space SP can be designed smaller than that of the head portion of the screw S2, and the total thickness of the distal end of the piston rod 21 a and the piston head 25 a can be designed small.

Also, the through-hole 26 a is formed a such a position as to release the head portion of the screw S1 protruding into the chamber 13 a. Therefore, the screw S1 avoids interfering with the piston head 25 a. Thus, even if the head portion of the screw S1 protrudes into the chamber 13 a, the through-hole 26 a releases the head portion of the screw S1, so the minimum of the capacity of the chamber 13 a can be small as much as possible, thereby ensuring the ratio of the maximum to the minimum of the capacity of the chamber 13 a. This can further introduce air into the crankcase 20. The screw S1 is an example of a cylinder side fixation member.

Next, a description will be given of a vacuum machine X according to a comparative example having structure different from the vacuum machine A. FIG. 5 is a partially sectional view of the vacuum machine X according to the comparative example, and FIG. 5 corresponds to FIG. 4. Additionally, similar components are designated with similar reference numerals and a duplicated description of those components will be omitted. The cylinder 10 x includes a cylinder body 12 x, a partition plate 14 x, a cylinder head 15 x. A check valve V1 x, arranged within a room 18 x and fixed to an outer surface of the partition plate 14 x by a screw not illustrated, permits air to pass to a chamber 13 x through a hole portion 16 x from the room 18 x, but restricts air from passing reversely. The check valve V2 x, arranged within the chamber 13 x and fixed to an inner surface of the partition plate 14 x by a screw not illustrated, permits air to pass to a room 19 x through a hole portion 17 x from chamber 13 x, but restricts air from passing reversely. A piston Px includes a piston rod 21 x, a piston head 25 x, and a sealing ring Cx. A space is not provided between the piston rod 21 x and the piston head 25 x.

Air is introduced into the chamber 13 x through an aperture Hx1, the room 18 x, and the hole portion 16 x by the reciprocation of the piston Px, and air is exhausted outside from the chamber 13 x through the hole portion 17 x, the room 19 x, and an aperture Hx2. In the vacuum machine X, air is not introduced into the crankcase 20 x. Thus, most of the flowing passage of air is the rooms 18 x and 19 x of the cylinder head 15 x located at the outer side of the vacuum machine X. For this reason, there is a certain limit to a decrease in leak of sound of air flowing. In the vacuum machine A according to the present embodiment, air flows through the crankcase 20 as illustrated in FIG. 4. This can suppress sound of air flowing through the crankcase 20 from being leaked, and can suppress the noise. Also, in the vacuum machine A according to the present embodiment, air flows from the narrow space chamber 13 a to the wide space crankcase 20, so the noise is suppressed by the operation similar to car mufflers.

Also, in a case where the vacuum machine X according to the comparative example has plural pairs of the cylinder body, the cylinder head, and the piston, it is considered that a passage for meeting air exhausted from the cylinder heads is provided outside the crankcase 20 x. However, in the vacuum machine A according to the present embodiment, air introduced from the cylinder heads 15 a to 15 d are met within the crankcase 20. For this reason, a special passage for meeting air is not needed. Thus, as for the vacuum machine A according to the present embodiment, an increase in the number of parts is suppressed, and an increase in size of the device is also suppressed.

Also, in the vacuum machine X according to the comparative example, air does not flow in the crankcase 20 x. In the vacuum machine A according to the present embodiment, air flows through the crankcase 20 and is exhausted outside from the nozzle N. Thus, the crankcase 20 can be cooled, and the heat degradation in parts of the crankcase 20 can be suppressed.

Next, a compressor A′ according to the present embodiment will be described. FIGS. 6 and 7 are front and rear views of the compressor A′, respectively. FIG. 6 corresponds to FIG. 1, and FIG. 7 corresponds to FIG. 3. Additionally, similar components are designated with similar reference numerals and a duplicated description of those components will be omitted. Unlike the vacuum machine A, in the compressor A′, air is introduced into the crankcase 20 through the nozzle N.

FIG. 8 is a partially enlarged view of FIG. 7. A partition plate 14 a′ is formed with a hole portion 16 a′ communicating the room 19 a with the chamber 13 a. The partition plate 14 a′ is not formed with a through-hole communicating the room 18 a with the chamber 13 a, but may be formed with a through-hole communicating the room 18 a with the chamber 13 a, and this through-hole may be sealed.

A check valve V1′ is fixed to the partition plate 14 a′. The check valve V1′ permits air to flow to the room 19 a through the hole portion 16 a′ from the chamber 13 a, but restrict air from flowing reversely. The check valve V1′ is fixed to an outer surface, of the partition plate 14 a′ facing the cylinder head 15 a, by a screw S1′. The screw S1′ and the hole portion 16 a′ are arranged in the central axis direction of the rotational shaft 42. Thus, the check valve V1′ is fixed to the partition plate 14 a′ in such a posture that the central axis direction of the rotational shaft 42 is the longer direction. A proximal end of the check valve V1′ is fixed to the partition plate 14 a′ by the screw S1′, a distal end of the check valve V1′ is a free end, and the check valve V1′ is elastically deformed so as to open and close the hole portion 16 a′. The check valve V1′ is elastically deformed by a difference in inner pressure between the chamber 13 a and a room 19 a, so the hole portion 16 a′ is opened and closed. The check valve V1′ is provided within the room 19 a.

A piston Pa′ includes: a piston rod 21 a′; a piston head 25 a′ fixed to a distal end of the piston rod 21 a′ by a screw not illustrated; and a seal ring C′ sandwiched between the piston rod 21 a′ and the piston head 25 a′. The check valve V2′ is fixed to a bottom surface, of the recess portion 23 a of the piston rod 21 a′ facing the piston head 25 a′, by a screw S2′. The screw S2′ is an example of a fixation member. A proximal end of the check valve V2′ is fixed to the piston rod 21 a′ by the screw S2′, a distal end of the check valve V2′ is a free end, and the check valve V2′ is elastically deformed to open and close the through-hole 22 a. The check valve V2′ is elastically deformed by a difference in inner pressure between the chamber 13 a and the crankcase 20, so that through-hole 22 a is opened and closed. The check valve V2′ is provided and is elastically deformable within the space SP. The check valve V2′ permits air to flow into the crankcase 20 through the through-hole 26 a, the space SP, and the through-hole 22 a from the chamber 13 a, but restrict air from flowing reversely.

When the capacity of the chamber 13 a is increased from the minimum by the reciprocation of the piston Pa′, the distal end of the check valve V2′ is elastically deformed to be bent away from the through-hole 22 a, which opens the through-hole 22 a. Thus, air introduced into the crankcase 20 through the nozzle N is introduced into the chamber 13 a through the through-hole 22 a, the space SP, and the through-hole 26 a. When the capacity of the chamber 13 a decreases from the maximum, the distal end of the check valve V1′ is elastically deformed to be bent away from the hole portion 16 a′, which opens the hole portion 16 a′. Thus, air is introduced into the room 19 a from the chamber 13 a, and is exhausted from the aperture Ha2.

When the distal end of the check valve V2′ is elastically deformed to be bent away from the through-hole 22 a, the distal end of the check valve V2′ abuts with an inner surface of the piston head 25 a′, so that the check valve V2′ is restricted from being further elastically deformed. Thus, the maximum amount of the elastic deformation of the check valve V2′ is restricted to a certain amount. This can suppress the deterioration in the performance of the check valve V2′ caused by a too large amount of the elastic deformation.

Also, the through-hole 26 a releases the screw S2′ fixing the check valve V2′. Specifically, the through-hole 26 a is formed coaxially with the screw S2′ so as not to interfere with a head portion of the screw S2′ protruding to the space SP. Therefore, for example, the thickness of the space SP can be designed smaller than that of the head portion of the screw S2′, and the total thickness of the distal end of the piston rod 21 a′ and the piston head 25 a′ can be designed small.

Also, the through-hole 26 a is formed at such a position as to release a lower end portion of the screw S1′ protruding into the chamber 13 a in accordance with the reciprocation of the piston Pa′. Therefore, the screw S1′ avoids interfering with the piston head 25 a. Thus, the minimum of the capacity of the chamber 13 a can be small as much as possible, thereby exhausting the large amount of air from the crankcase 20. The screw S1′ is an example of a cylinder side fixation member.

Next, a description will be given of a compressor X′ according to a comparative example having structure different from the compressor A′. FIG. 9 is a partially sectional view of the compressor X′ according to the comparative example. FIG. 9 is the partially sectional view of a side view of the compressor X′, and illustrates the compressor X′ when viewed along the cross section parallel with a rotational shaft. An upper portion of the compressor X′ is located at the left side of FIG. 9, and the bottom side is located at the right side of FIG. 9. Additionally, similar components are designated with similar reference numerals and a duplicated description of those components will be omitted. A cylinder 10 x′ includes a cylinder body 12 x′, a partition plate 14 x′, and a cylinder head 15 x′. A check valve V1 x′, arranged within a room 19 x′ and fixed to an outer surface of the partition plate 14 x′ by a screw not illustrated, permits air to pass to a chamber 19 x′ through a hole portion 17 x′ from the room 13 x′, but restricts air from passing reversely. A check valve V2 x′, arranged within the chamber 13 x′ and fixed to an outer surface of the piston head 25 x′ by a screw S2 x′, permits air to pass to a chamber 13 x′ from a crankcase 20 x′, but restricts air from flowing reversely. The piston Px′ includes a piston rod 21 x′,a piston head 25 x′, and a seal ring Cx′. The space is not provided between the piston rod 21 x′ and the piston head 25 x′. Through-holes 22 x′ are 26 x′ directly communicate with each other.

Air is introduced into the chamber 13 x′ through the through-holes 22 x′ and 26 x′ from the crankcase 20 x′ by the reciprocation of the piston Px′, and air is exhausted outside from an aperture Hx2′ through the hole portion 17 x′ and the room 19 x′. As illustrated in FIG. 9, the check valve V2 x′ is fixed to the outer surface of the piston head 25 x′. Thus, when a capacity of the chamber 13 x′ increases, a distal end of the check valve V2 x′ is elastically deformed to be bent away from the through-hole 26 x′. At this time, the amount of the elastic deformation of the check valve V2 x′ cannot be restricted. Thus, the amount of the elastic of deformation of the check valve V2 x′ might be large, and the performance might deteriorate.

Also, the check valve V2 x′ is elastically deformed such that its distal end abuts with an inner surface of the partition plate 14 x′, so that contact noise might be made. In particular, when the piston Px′ reciprocates at high speed, the amount of the elastic deformation of the check valve V2 x′ increases and the distal end of the check valve V2 x′ abuts with the inner surface of the partition plate 14 x′ in accordance with the reciprocation of the piston Px′, which might increases the noise. In the compressor A′ according to the present embodiment, the maximum amount of the elastic deformation of the check valve V2′ is restricted to be a certain amount, which can also suppress an increase in the contact noise of the piston head 25 a′ and the check valve V2′.

Also, the check valve V2 x′ is fixed to the outer surface of the piston head 25 x′ facing the inner surface of the partition plate 14 x′. Therefore, in consideration of a position, a size, and a shape of the check valve V2 x′, a shape of an inner surface of the partition plate 14 x′ facing the check valve V2 x′ has to be designed. In contrast, in the compressor A′ according to the present embodiment, the check valve V2′ is arranged between the piston head 25 a′ and the piston rod 21 a′, so the check valve V2′ does not abut with the partition plate 14 a′. Thus, regardless of a position, a size, and a shape of the check valve V2′, the shape of the inner surface of the partition plate 14 a′ can be designed. Accordingly, the freedom degree of the design of the partition plate 14 a′ improves.

While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention.

The vacuum machine A and the compressor A′ according to the present embodiment each has four pairs of the cylinders 10 a to 10 d and pistons, but are not limited to these. The vacuum machine and the compressor each may have only one pair, two pairs, or three pairs of the cylinders and pistons, and may have five or more pairs of the cylinders and pistons.

The vacuum machine A according to the present embodiment functions as a compressor, when an object product is connected to the nozzle N that exhausts air. The compressor A′ according to the present embodiment functions as a vacuum machine, when an object product is connected to the nozzle N that intakes air.

Note that, in the present embodiment, subject matters of additional notes to be described later are supported. The subject matters of the additional notes will be explained below.

There is known a vacuum machine in which a capacity of a chamber increases depending on reciprocation of a piston within a cylinder body fixed to a crankcase and in which air is sent from an intake room to an exhaust room through this chamber. Japanese Patent Application Publication No. 2008-95700 discloses a related device.

The cylinder head is arranged in the outside of the crankcase, and air flows to the exhaust room through the chamber from the intake room in the cylinder head. In this way, a flowing passage of air is mainly located at the outside of the crankcase, so that there is a certain limit to a decrease in leak of sound of air flowing.

According to an aspect of following additional notes, there are provided a vacuum machine and a compressor in which noise is restricted.

(additional note 1)

1. A vacuum machine or a compressor comprising:

a crankcase;

a cylinder body fixed to the crankcase;

a cylinder head fixed to a distal end of the cylinder body; and

a piston reciprocating within the cylinder body,

wherein

the piston includes:

-   -   a piston rod; a piston head fixed to a distal end of the piston         rod and defining a chamber in cooperation with the cylinder body         and the cylinder head; and     -   a check valve arranged within a space formed between the piston         rod and the piston head,

the piston rod and the piston head each includes a through-hole communicating with the space, and

the check valve is elastically deformed within the space so as to open and close the through-hole of the piston rod or the piston head, permits air to flow from one of the chamber and the crankcase to the other one of the chamber and the crankcase through the through-holes of the piston rod and the piston head and the space, and restrict air from flowing to the other one of the chamber and the crankcase from the one of the chamber and the crankcase.

(additional note 2)

2. The vacuum machine or the compressor of additional note 1 comprising a plural pairs of the cylinder body, the cylinder head, and the piston. 

What is claimed is:
 1. A vacuum machine comprising: a crankcase; a cylinder body fixed to the crankcase; a cylinder head fixed to a distal end of the cylinder body; and a piston reciprocating within the cylinder body, wherein the piston includes: a piston rod; a piston head fixed to a distal end of the piston rod and defining a chamber in cooperation with the cylinder body and the cylinder head; and a check valve arranged within a space formed between the piston rod and the piston head, the piston rod and the piston head each includes a through-hole communicating with the space, and the check valve is elastically deformable within the space so as to open and close one of the through holes of the piston rod and the piston head.
 2. The vacuum machine of claim 1, wherein the check valve abuts with the one of the piston rod and the piston head to close the one of the through holes of the piston rod and the piston head, and is elastically deformed away from the one of the through holes of the piston rod and the piston head and closer to the other one of the through holes of the piston rod and the piston head to open the one of the through holes of the piston rod and the piston head.
 3. The vacuum machine of claim 1, wherein the check valve is fixed to the one of the piston rod and the piston head by a fixation member, and the other one of the through-holes of the piston rod and the piston head releases the fixation member.
 4. The vacuum machine of claim 1, wherein the cylinder head includes a partition wall portion defining the chamber in cooperation with the piston head, the partition wall portion is formed with a communication hole communicating with the chamber, an opening and closing member opening and closing the communication hole being fixed to the partition wall portion by a cylinder side fixation member, and the through-hole of the piston head releases the cylinder side fixation member projecting in the chamber in accordance with reciprocation of the piston head.
 5. A compressor comprising: a crankcase; a cylinder body fixed to the crankcase; a cylinder head fixed to a distal end of the cylinder body; and a piston reciprocating within the cylinder body, wherein the piston includes: a piston rod; a piston head fixed to a distal end of the piston rod and defining a chamber in cooperation with the cylinder body and the cylinder head; and a check valve arranged within a space formed between the piston rod and the piston head, the piston rod and the piston head each includes a through-hole communicating with the space, and the check valve is elastically deformable within the space so as to open and close one of the through holes of the piston rod and the piston head.
 6. The compressor of claim 5, wherein the check valve abuts with the one of the piston rod and the piston head to close the one of the through holes of the piston rod and the piston head, and is elastically deformed away from the one of the through holes of the piston rod and the piston head and closer to the other one of the through holes of the piston rod and the piston head to open the one of the through holes of the piston rod and the piston head.
 7. The compressor of claim 5, wherein the check valve is fixed to the one of the piston rod and the piston head by a fixation member, and the other one of the through-holes of the piston rod and the piston head releases the fixation member.
 8. The compressor of claim 5, wherein the cylinder head includes a partition wall portion defining the chamber in cooperation with the piston head, the partition wall portion is formed with a communication hole communicating with the chamber, an opening and closing member opening and closing the communication hole being fixed to the partition wall portion by a cylinder side fixation member, and the through-hole of the piston head releases the cylinder side fixation member projecting in the chamber in accordance with reciprocation of the piston head.
 9. A piston comprising: a piston rod; a piston head fixed to a distal end of the piston rod; and a check valve arranged within a space formed between the piston rod and the piston head, wherein the piston rod and the piston head each includes a through-hole communicating with the space, and the check valve is elastically deformable within the space so as to open and close one of the through holes of the piston rod and the piston head. 